How Resilient Position, Navigation and Timing can INSPIRe greater confidence in the Blue Economy
12 05 2023

By Phil Buckley (Associate Director, NLA International) on behalf of the INSPIRe team.

The Blue Economy is underpinned by an oft-overlooked but critical capability. Since the very first humans set out to sea the ability to understand position and time has allowed navigation. Local knowledge and familiarity with coastal terrain was supplemented by advances in knowledge and then technology. Astronavigation, the compass, Harrison’s clocks – all steps in the evolution of our ability to be increasingly precise about where and when we are whilst at sea. Space technology now gives us what many call GPS or GNSS (Global Navigation Satellite System) and many of us – on land and sea – put our unwavering faith in this solution.

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As humans advance Blue Economies, we are deploying more – and ever-more innovative – infrastructure at sea. Offshore wind has grown rapidly over the last 20 years and looks set to continue its upward surge in the coming years, as this week’s announcement of plans for a new $4.7 Billion offshore wind turbine assembly hub in California attest. Aquaculture fish farms are now the source of more fish protein than wild caught fish, with precision aquaculture employing computer vision and Artificial Intelligence to monitor and manage stock growth and advanced disease management systems to promote greater efficiency. We ship more goods to more ports than ever before, with smart ports investing heavily in technological infrastructure, as evidenced by the Port of Antwerp’s recent introduction of six autonomous drones as part of their security measures. Autonomous vessels are also becoming more prevalent at sea, from underwater covert intelligence-gathering to hydrographic data acquisition.

The seas, therefore, have never been busier or more complex and so it is crucial that we ask the question – to what extent can users really trust the position, speed, heading and time displayed by their electronic chart or ‘satnav’? How confident should users be when making decision based on this information? And what fallback mechanisms might be required for the exponentially growing army of remote and autonomous applications? In other words, what is the integrity of the system?

Tailor Airey leading an 18 month project exploring Integrated Navigation as a System of systems for PNT Resilience (INSPIRe) to define practical measures that could be implemented to quantify the level of confidence a user should have in their PNT solution. INSPIRe is funded by the European Space Agency’s Navigation Innovation and Support Programme (NAVISP) and builds on the earlier NAVISP-funded MarRINav project led by Blue Economy solutions company NLA International.

An Integrity measure will tell the user if their PNT data is sufficiently reliable to be used for the manoeuvres in progress at the time and warn the user if it is not. GNSS integrity is seen to have two components: system level integrity and user level integrity. System integrity would indicate any compromise in the raw signals transmitted by the satellites and user level integrity would detect signal degradation at the point of use caused by local factors such as multipath reflections from port infrastructure.

Integrity should not be confused with accuracy: an imprecise position may in some circumstances be useful if integrity measures can reliably assure the user that the true position lies within a defined boundary to a defined confidence level.

We know of examples from the automotive sector where positioning systems provide dangerously false assurances that location accuracies are within defined limits. A critical requirement for INSPIRe is that integrity indications must themselves be trustworthy.

The project is studying RAIM (Receiver Autonomous integrity Monitoring) algorithms for single and dual frequency GPS, and dual frequency multi-constellation (DFMC) GNSS. INSPIRe will also study EGNOS (European Geostationary Navigation Overlay Service) monitoring, RAIM availability prediction, a DFMC integrity monitor and feasibility of using signals of opportunity to improve integrity.

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We are working with the team studying a possible Space-Based Augmentation System to align INSPIRe to that project. It was also encouraging to see these issues featured in a Ministerial update to the UK's Parliament recently, reflecting on cross-Governmental developments; all relevant activities must continue to seek to complement each other.

The INSPIRe team have been proactive to engage with end users in the Blue Economy and maritime space. Stakeholders have confirmed that there is some awareness of the importance of integrity metrics needed to provide assurance that GNSS positions are safe to use. Many participants at a recent workshop could cite personal experience of GNSS outages.

We all know and love the blue circle depicting error limits on Google Maps, but typically the area encompassed by a particular limit will be a more complex shape such as an ellipse or “cocked hat”. Mariners we consulted said they would find a spatially accurate representation of position error bounds useful to complement a simple ‘traffic light’ indication.

A system to improve integrity must provide value to the user, so the project will perform a cost benefit analysis to quantify this and will propose routes to implementation.

We would always like to hear from those with an interest in PNT integrity and the value of accurate integrity information, or views on how that information should be provided to users.

Contact us to get involved and sign up for project newsletters through the website:

To learn more about the importance of PNT in Blue Economies write to

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